Ryanair
Ryanair only cancel flights if the inbound a/c is diverted to another airport due to reasons outside of there control eg, weather, runway closure, night flying ban etc and not all diverted flights are cancelled.
If a Ryanair a/c has a tecional problem the flight will be delayed until it has been resolved or another a/c which is not been used has arrived from Ryanair's main bases in Dublin or London Stansted and on very few times it will be cancelled.
Also if a Ryanair flights from a non base airport is delayed by a tec problem and If there is a flight due to arrive from Dublin or London Stansted and the delayed flight is awaiting for engineers to arrive ryanair will us the a/c which arrived from Dublin or London Standsted to operate the delayed flight and Dublin and London Stansted will be delayed until the a/c has been fixed.